The technology generally relates to capacitance measuring circuits for measuring capacitance of an electrode. Capacitance measurement is used in many applications including capacitive touch screens, digital styluses, pressure sensors and others.
Accuracy of capacitance measurements affects the quality of the application concerned such as the quality of control of a graphical user interface a user can achieve via a touch screen, or the accuracy of estimation of the density of a gas in a container where the pressure is measured by a pressure sensor. Accuracy is affected by many factors including noise, changes in temperature, changes in humidity and other factors.
The resolution of the capacitance measurements also affects the quality of the application where the capacitance measurements are being used. If the resolution is too coarse then low capacitance touch events may be interpreted as the absence of a touch event by a capacitive touch screen. If the resolution is too coarse then small differences in pressure may be undetected by a pressure sensor using capacitance. Resolution is affected by many factors including the design of the capacitance measurement circuit and the environment of the electrode.
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known capacitance measuring circuits.